A sialon sintered body is recognized as a material that has excellent hardness, has high strength in a temperature range of room temperature to a high temperature, and has high chemical stability than silicon nitride. Therefore, a wide range of applications of the sialon sintered body, such as a machine part, a heat resistant part, and a wear resistant part, is expected. One of the applications of the sialon sintered body is a cutting insert that is attached to a cutting tool (for example, refer to Patent Literatures 1 to 5). The cutting insert is a cutting edge detachably attached to the tip end of a main body of the cutting tool and is a tool part that is also referred to as a throw-away tip, a cutting edge replaceable tip or the like.